Acknowledgements
Last updated 3 November 2026
Back2Back itself
The Back2Back app, this website and the service behind them are © 2026 Back2Back. All rights reserved. The components listed below are other people’s, used under their own licences.
Trademarks, and who Back2Back is not
Back2Back is independent software. It is not made, endorsed, certified or supported by AlphaTheta Corporation, Pioneer DJ or Pioneer Corporation, and none of them has any responsibility for it.
Pioneer DJ, AlphaTheta, CDJ, DJM, rekordbox and PRO DJ LINK are trademarks or registered trademarks of their respective owners. Apple, Mac and macOS are trademarks of Apple Inc. They are named on this website and in the app only to say what Back2Back works with.
ASIO is a trademark of Steinberg Media Technologies GmbH. Back2Back is not made, endorsed or certified by Steinberg and contains none of its software. On Windows the app lists a mixer’s driver under the name the mixer’s maker gave it, which is the only place that word appears.
The work this stands on
Back2Back owes a debt to Deep Symmetry (James Elliott and contributors) for years of careful, public research into the PRO DJ LINK protocol, published in their Packet Analysis and their open-source libraries. Back2Back’s PRO DJ LINK code was written from that research and from measuring real players, and two of its files were translated from their code: the one that takes a device number on the network, from beat-link, and a metronome, from electro. Those two files are © Deep Symmetry, LLC, with Back2Back’s changes, and are under the Eclipse Public License 2.0 rather than Back2Back’s own terms: their source code is printed in full, with the licence, in the full notices below, and you may use them under it. Nothing else in Back2Back is under that licence, and Deep Symmetry has nothing to do with Back2Back. Thank you.
Open-source software
Back2Back is built with open-source software, used under its own licences. The main components:
| Component | Used for | Licence |
|---|---|---|
| beat-link and electro (Deep Symmetry) | Two files of the app’s PRO DJ LINK code are translated from them (above); their source is in the full notices | Eclipse Public License 2.0 |
| LiveKit (server, Rust SDK and browser client) | Audio transport | Apache License 2.0 |
| WebRTC (libwebrtc) | Real-time audio and the Opus codec | BSD 3-Clause |
| Tauri | The desktop app’s window and packaging | MIT or Apache License 2.0 |
| Tokio, axum, hyper, serde and the wider Rust ecosystem | The app’s and the server’s foundations | MIT or Apache License 2.0 |
| SQLite, through rusqlite | The account database | Public domain; MIT |
| cpal | Audio input and output | Apache License 2.0 |
| Symphonia | Reading audio files | Mozilla Public License 2.0 (used unmodified; its source is at github.com/pdeljanov/Symphonia) |
| Signalsmith Stretch and Signalsmith Linear | Master Tempo in the MIDI version: changing a track’s tempo without changing its pitch | MIT |
| midir | Talking to MIDI controllers | MIT |
| flacenc | Recording a set as FLAC, where the server is set to | Apache License 2.0 |
| LAME | Recording a set as MP3, on the server | GNU Lesser General Public License 2.0 or later (used unmodified; its source is at lame.sourceforge.io) |
| lettre | Sending email | MIT |
| Caddy | HTTPS | Apache License 2.0 |
| Archivo, by Omnibus-Type | The typeface, in the app and on this website | SIL Open Font License 1.1 |
Every open-source package in the app and on the server, with the licence each is under, is in
the full list, and the text of every licence, as each asks, is in
the full notices; the app carries them in its bundle too, as
THIRD-PARTY-NOTICES.txt, all but the part about this website. Each remains the property of its authors, and none of them endorses
Back2Back.